Forced flow generator and method of operating same



March 9, 1937.

H. J. KERR FORCED FLOW GENERATOR AND METHOD OF OPERATING SAME OriginalFiled May 7, 1930 3 Sheets-Sheet l 3 8 l E g f 1 4 13 J3 L It 11 p1 3Lii;

INVENTOR Howard J Kerr BY \R ALI'IORNEY 122. UQUiD mms udmm \JAPQQEZFRS.

March 9, 1937. H. J. KERR 2,072,887

FORCED FLOW GENERATOR AND METHOD OF OPERATING SAME Original Filed May'7, 1930 5 Sheets-Sheet 2 izz LEQUHJ Rmt m March 9, 1937. H. J. KERR2,072,887

FORCED FLOW GENERATOR AND METHOD OF OPERATING SAME Original Filed May 7,1930 3 Sheets-Sheet 3 INVENTOR. Howard J. Kerr 22l lithium.

& VAPORlZERS,

Patented Mar. 9, 1937 UNITED STATES PATENT OFFICE FORCED FLOW GENERATORAND METHOD OF OPERATING SAME Howard J. Kerr, Westfield, N. J., assignorto The Babcock & Wilcox Company, Bayonne, N. J., a corporation of NewJersey Serial No. c2 3 g 10 Claims.

ing superheated vapors in a vapor generator of the type in which aliquid enters at one end of a tube and emerges from the other end as avapor or gas; this present application being a continuation of myprevious application filed May 7, 1930, Serial Number 450,348.

The present invention, however, is distinguished from the well knownflash or semi-flash generator methods in that it comprises utilizing apath, or paths, of extreme length and small bore into which liquiddistributed at one end, extends therethrough for a preponderance of thelength of such path and at regulated locations therein, dependent uponcontrolled conditions of water feed and combustion, is preheated,vaporized and superheated in the quantity and quality required to meetspecific load conditions, all of which is accomplished withoutinterposition of any separation of liquid and vapor in a drum or thelike.

Also, a feature of the present invention is the distribution, for theequalization of flow and temperature, of the fluid at one or severalpoints along the flow path as, for instance, bringing the flow fromseveral paths together in a mixing or equalizing header and theredistributing to a multiplicity of paths, such mixing and distributionpreferably being carried out at locations where there is no change inthe physical state of the fluid, thereby avoiding the dimculties whichwould be encountered in endeavoring to mix fluids of unlike physicalproperties as, for instance, steam and water.

' In a preferred form the generator for the method of the presentinvention is typified by a multiplicity of long small-bore fluid-flowconduits arranged in parallel and presenting an uninterrupted state offlow from liquid inlet at one end to vapor outlet at the other, withmeans incorporated in the flow path intermediate the inlet and outletfor mixing the fluid of the several paths to establish an equilibrium ofphysical condition, and to then re-apportion the fluid flow throughseveral paths.

The invention particularly relates to a once through" steam boilermethod of operation that can be practiced at very high pressures, up to,or above, the criti cg.l,pr e s s ure gf steam. By a once throughboiTei'T is meant a'-boiler into which feed water enters and is entirelyevaporated to generate steam without any of the water returning to theinlet of the boiler before it is evaporated and the steam passed to aplace of use. In this type of boiler the water is forced through thevarious sections by means of the feed pump.

This invention relates to a method of generat- Y The boiler is providedwith an economizer section where the feed Water is heated while it flowsin a counter-current direction to the direction of flow of the heatinggases to a point beyond which steam is generated. The heated water thenpasses to the boiler section where all of it is vaporized, the steamthen passes to a superheater where it is superheated before it iscarried to the place of use.

In order to permit the use of very high pressures, say up to thecritical pressure of steam, it is necessary to dispense with cast ironparts in a boiler and to use small tubes, preferably made of seamlesswrought steel with the connections between the tubes welded. In order toprevent the frictional resistance through the boiler from becoming toohigh with the small tubes which are connected in series, it is sometimesnecessary to use two or more tubes grouped in parallel, the groups beingconnected in series.

Also since the demand for steam may vary rapidly, requiring acorresponding rapid variation in the amount of water fed to the boilerand heat transferred to the water, it is desirable to obviate thepresence of large masses of material, such as thick refractory furnacewalls, for example, where large quantities of heat might become storedand be transmitted to the water when it is not required. For this reasonit is desirable to surround the furnace, or a substantial portionthereof, with steam generating tubes of the boiler to absorb the radiantheat of the furnace and prevent the storage of too much heat in partswhere it would interfere with the desired change in the rate of steamgeneration.

In the boiler described in this application the amount of feed water isvaried in accordance with the demand for the steam and the firing of theboiler is to be varied so as to keep the outlet temperature of the steamat the desired point. The desired pressure of the steam is maintained bythe proper variation of the amount of feed water and fuel.

In the accompanying drawings:

. Figure 1 is a vertical sectional view, somewhat diagrammatical of avaporizer constructed in accordance with the present invention.

Fig. 2 is a transverse section on the line 2-2 of Fig. 1.

Fig. 3 is a transverse section of a modified arrangement of tubes in theplane represented l by the line 3-3 of Fig. 1.

Fig. 4 is a somewhat diagrammatic view, simiiar to Fig. 1, showing thevaporizer partially in trance end to the header I0.

section, and with the controls for water input and elements ofcombustion.

In the drawings reference character I indicates a furnace that may befired by one or more burners 2 that are shown located at the bottom ofthe furnace. A flue 3 extends from the upper portion of the furnace tothe stack 4.

The feed water pipe 5 enters a distributing and equalizing header 6 nearthe upper portion of the flue 3. One or more long small bore tubes leadfrom the header 6 to the economizer section 1 of the boiler that islocated in the upper portion of the flue 3. The economizer I may consistof coils of small seamless, wrought steel tubes in parallel, or may bemade up of parallel tubes subdivided by headers into small groups, thegroups being connected in series, and the total series connected groupthen joined'to the header 8, the coils or groups of tubes constitutingthe economizer are connected so that the water passes through themcounter-current to the gases in the flue 3 and the outlet ends of theeconomizer coils or groups of tubes are connected to a header 8 outsideof the flue. The header 8 is connected by means of the pipe 9 to aheader I located outside of the wall of the furnace I.

One or more tubes extend from the header ID to the steam generatingtubes or boiler section I I. This section preferably comprises coils ortubes surrounding the furnace I to shield the walls thereof from theradiant heat of the furnace and prevent a large amount of heat frombeing stored in walls of the furnace. In addition to the coils or tubesof the steam generating section which shield the furnace walls form theintense heat, the steam generating or boiler section may compriseadditiona l tgbes which extend across the furnaceftli'ese es a so beingconnected in series or in groups in parallel with the tubes in eachgroup connected in series. The tubes referred to in the steam generatingsection, in addition to the coils heated by radiant heat, may bearranged across the furnace in the manner shown 1% which isrepresentative of a section in any location in the steam generatingsection similar to the plane represented by the line 3--3 of Fig. 1 fromthe lowermost portion of the steam generating section II to theuppermost portion thereof, if desired, it being obvious that in the caseof such an arrangement the lowermost of these transverse gpils would besubjected to radiant lfifi' 'ffie vapor or steam generating section IIis comprised of a plurality of tubes coiled in parallel and eachconnected at its fluid en- The steam and water in the section I I areshown to flow parallel to the direction of the hot gases, so that if thesteaming temperature of the water has not been reached in the economizersection I, the coolest portions of these tubes are exposed to thehottest gases. This steam generating section is so constructed thatthere is an upflow of water and steam to obviate any danger of steampockets,

forming which might be the case if the water and steam were made to flowdownwardly.

The outlet ends of the tubes of the steam generating or boiler section II are connected in series to coils or groups of tubes constituting thesuperheater I2 which is constructed in a manner similar to thatdescribed above in connection with the economizer I. The superheater I2is located in the flue 3 between the economizer I and boiler II. Thesteam to be heated in the superheater I2 flows in the same direction asthe gases which heat the economizer. The outlet ends of the superheatercoils or groups of tubes I2 are connected to the header l3 from which apipe I4 provided with a valve I5 leads to a steam main or place of steamconsumption. In connection with Fig. 2 and the section line 2-2 of Fig.1, it is to be understood that, if desirable, all of the coils in thissuperheater section may be of the type represented in this figure, orthat such coils may be located at any suitable zones therein, and it isto be noted that the actual superheating may take place only in theuppermost portion of this section I2 and after the steam becomes driedin the section I2.

A feed water pipe I6 leads from a condenser or hot well (not shown) tothe inlet of a feed pump I! which is preferably a triplex plunger pumpdriven in any convenient way. The pipe 5 leads from the outlet side ofthe pump II to the header 6 of the economizer I.

A bypass I8 having a valve I9 may be provided around the pump l1, and amake up feed water pipe 20 having a valve 2| may be connected to thepipe I6.

Portions of the coils II are extended as shown at 22 to enter thesetting of the steam generator and thereby form supports.

In Fig. 4 an orifice or similar element is located between the flanges22, creating a pressure differential bearing a known relation to rate ofvapor outflow. Such pressure differential is effective, through pipes23, to continuously position a regulating valve I9 in the by-passI8,'thereby automatically regulating liquid supply in accord ance withthe demand upon the generator. A bulb 24, sensitive to vapor outflowtemperature, forms part of a thermostat system of which 25 indicates theconnecting capillary continuously positioning the fuel regulating valve26 to maintain desired vapor outflow temperature. Should vapor outflowpressure depart from desired value, a readjustment of liquid inflow andof fuel supply rate is automatically accomplished in the desireddirection and amount, through the agency of regulating valves 2| and 21,both positioned directly by such pressure effective through the pipe 28.

When the demand upon the generator increases, the increased rate ofvapor outflow causes a throttling of valve I9, with consequent increasein rate of liquid inflow. Should the.

temperature of the vapor fall below desired value, the valve 26 will beopened proportionately to increase the heating; while if vapor pressureat the same time decreases below desired value the auxiliary fuel supplyvalve 21 will be positioned in an opening direction and thesupplementary liquid supply valve 2| will be positioned in necessarydirection and amount to cause the pressure to return to normal. Thesevarious regulations are quite independent in action and may act insequence or simultaneously, to correct the variables under control.

While a specific construction of a once-through boiler has beenillustrated and described in connection with the method of the presentinvention, it will be understood that other constructions employing thesame method of operation come Within the scope of this invention. Alsowhile different portions of the boiler have been described aseconomizer, boiler, and superheater sections, it will be clear that thelines of demarcation between these various sections are not definitelyfixed, but will vary depending upon the operation of the boiler, but inall cases the feed water will enter the economizer and after (itVAPORSZERS,

passing through the once-through" sections in series will leave thelast, or super-heater section, as superheated steam.

I claim- 1. A method of generating superheated vapor in a vaporizerincluding a furnace and a flow path continuous from fluid inlet tosuperheated vapor outlet and composed of a plurality of long, small-borefluid flow conduit portions arranged for flow in parallel, said pathincluding a steam generating and a superheating portion, said vaporizerhaving fluid forced therethrough from liquid inlet to superheated vaporoutlet, which comprises supplying working medium to the vaporizer at apressure substantially higher than the desired working pressure of thesuperheated vapor, utilizing the difference between supply and workingpressures to force said working medium through the vaporizer withcontinuously decreasing pressure from inlet to outlet, said flow pathhaving an extremely large ratio of surface to cross-section, releasingheat by combustion of fuel in the furnace and passing the gaseousproducts in heat transfer relation to said flow path at heat releaserate and gas flow rate sufficiently high in relation to the ratio ofsurface to crosssection of said flow path to evaporate and superheatsaid working medium in said flow path before it issues from the endthereof, and equalizing the heat content per pound of working mediumentering the several conduit portions in parallel intermediate thevaporizer inlet and outlet with respect to following conduit portionsand at a location in advance of the superheating portion of the flowpath.

2. A method of generating superheated vapor in a vaporizer including afurnace and a flow path continuous from fluid inlet to superheated vaporoutlet and composed of a plurality of long, small-bore fluid flowconduit portions arranged for flow in parallel, said path including asteam generating and a superheating portion, said vaporizer having fluidforced therethrough from liquid inlet to superheated vapor outlet, whichcomprises supplying working medium to the vaporizer at a pressure belowcritical and substantially higher than the desired working pressure ofthe superheated vapor, utilizing the difference between supply andworking pressures to force said working medium through the vaporizerwith continuously decreasing pressure from inlet to outlet, said flowpath having an extremely large ratio of surface to crosssection,releasing heat by combustion of fuel in the furnace and passing thegaseous products in heat transfer relation to said flow path at heatrelease rate and gas flow rate sufficiently high in relation to theratio of surface to cross-section of said flow path to evaporate andsuperheat said working medium in said flow path before it issues fromthe end thereof, and equalizing the heat content per pound of workingmedium entering the several conduit portions in parallel intermediatethe vaporizer inlet and outlet with respect to following conduitportions and at a location in advance of the superheating portion of theflow path.

3. A method of generating superheated vapor in a vaporizer including afurnace and a flow path continuous from fluid inlet to superheated vaporoutlet and composed of a plurality of long, small-bore fluid flowconduit portions arranged for flow in parallel, said path including asteam generating and a superheating portion, said vaporizer having fluidforced theretlir. .12.

LXdliiilibi liquid inlet to superheated vapor outlet of the vaporizer,which comprises supplying working medium to the vaporizer at a pressuresubstantially higher than the desired working pressure of thesuperheated vapor, utilizing the difference between supply and workingpressures to force said working medium through the vaporizer withcontinuously decreasing pressure from inlet to outlet, said flow pathhaving an extremely large ratio of surface to cross-section, releasingheat by combustion of fuel in the furnace and passing the gaseousproducts in heat transfer relation to said flow path at heat releaserate and gas flow rate sufficiently high in relation to the ratio ofsurface to cross-section of said flow path to evaporate and superheatsaid working medium in said flow path before it issues from the endthereof, and equalizing the heat content per pound of working mediumentering the several conduit portions in parallel intermediate thevaporizer inlet and outlet with respect to following conduit portionsand at a location in advance of the superheating portion of the flowpath and outside of the heating zone.

4. A method of operating a vaporizer to generate superheated vapor, saidvaporizer includ ing a fuel fired furnace and a flow path continuousfrom liquid inlet to superheated vapor outlet and composed of aplurality of long smallbore fluid flow conduit portions arranged forflow in parallel and having an extremely large ratio of heat absorbingsurface to cross-section, said path including vapor generating andsuperheating portions, and having fluid forced therethrough from liquidinlet to superheated vapor outlet by a positive displacement pump means,which comprises operating the pump means to positively displace a supplyof working medium to the vaporizer at a pressure substantially higherthan the desired working pressure of the superheated vapor, utilizingthe difference between supply and working pressures to force saidworking medium through the vaporizer with continuously decreasingpressure from inlet to outlet of said flow path, releasing heat bycombustion of fuel in the furnace without a solid fuel bed, passing thegaseous products in heat transfer relation to said flow path at heatrelease rate and gas flow rate sufficiently high in relation to theratio of surface to cross-section of said flow path to evaporate andsuperheat the working medium passing from the outlet of the superheaterportion of the flow path, equalizing the heat content per pound ofworking medium entering the several conduit portions in parallelintermediate the vaporizer inlet and outlet and at a location in advanceof the superheating portion of the flow path, and controlling thequantity of liquid delivered to the flow path independent of the rate ofdisplacement of the aforesaid pump means.

5. A method of operating a vaporizer to generate superheated vapor, saidvaporizer including a fuel fired furnace and a flow path continuous fromliquid inlet to superheated vapor outlet and composed of a plurality oflong small-bore fluid flow conduit portions arranged for flow inparallel and having an extremely large ratio of heat absorbing surfaceto cross-section, said path including vapor generating andsuperheatingportions, and having fluid forced therethrough from liquidinlet to superheated vapor outlet by a positive displacement pump means,which comprises'operating the pump means to positively displace a supplyof working medium to the vaporizer at a pressure substantially higherthan the desired working pressure of the superheated vapor, utilizingthe difference between supply and workingpressures to force said workingmedium 5 through the vaporizer with continuously decreasing pressurefrom inlet to outlet of said flow path, releasing heat by combustion offuel in the furnace without a solid fuel bed, passing the gaseousproducts in heat transfer relation to said flow l0 path at heat releaserate and gas flow rate sufficiently high in relation to the ratio ofsurface to cross-section of said flow path to evaporate and superheatthe working medium passing from the outlet of the superheater portion ofthe flow path, equalizing the heat content per pound of working mediumentering the several conduit portions in parallel intermediate thevaporizer inlet and outlet and at a location in advance of thesuperheating portion of the flow path and remote 0 from the heat of thecombustion gases, and controlling the quantity of liquid delivered tothe flow path independent of the rate of displacement of the aforesaidpump means.

6. A vapor generator comprising a furnace, a

fluid flow passage continuous from liquid inlet to superheated vaporoutlet and composed of a plurality of long small-bore fluid flow conduitportions arranged for flow in parallel and having an extremely largeratio of heat absorbing surface to cross-section, said path includingvapor generating and superheating portions, means flring the furnacewith elements of combustion in a manner incapable of forming a.substantial fuel bed and operable at a heat release rate and gas flowrate sufficiently high in relation to the ratio of surface tocross-section of said flow passage to evaporate and superheat the fluidbefore passing from the superheater outlet, means at a location inadvance of the superheating portion of the 0 flow path and combining thefluid flow from a plurality of conduit portions for equalization of theheat content per pound of working fluid, displacement pump meansarranged to supply liquid positively to the generator at a pressuresubstantially higher than the desired working pressure of thesuperheated vapor whereby the difference between supply and workingpressures forces the fluid through the fluid flow passage with acontinuously decreasing pressure from liquid inlet to vapor outlet andwith the pressure quantity relation of the liquid supply normallyunaffected by a change in pressure in the flow path, and means forvarying the quantity of liquid delivered to the flow passage independentof the rate of displacement of said pump means.

7. A vapor generator comprising a furnace, a fluid flow passagecontinuous from liquid inlet to superheated vapor outlet and composed ofa plurality of long small-bore fluid flow conduit portions arranged forflow in parallel and having an extremely large ratio of heat absorbingsurface to cross-section, said path including vapor generating andsuperheating portions, means firing the furnace with elements ofcombustion in a manner incapable of forming a substantial fuel bed andoperable at a heat release rate and gas flow rate sufficiently high inrelation to the ratio of surface to cross-section of said flow passageto evaporate and superheat the fluid before passing from the superheateroutlet, means at a location remote from the heat of the combustion gasesand in advance of the superheating portion of the flow path andcombining the fluid flow from a plurality of conduit portions forequalization of the heat content per pound of working fluid,

displacement pump means arranged to supply liquid positively to thegenerator at a pressure substantially higher than the desired workingpressure of the superheated vapor whereby the difference between supplyand working pressures forces the fluid through the fluid flow passagewith a continuously decreasing pressure from liquid inlet to vaporoutlet and with the pressure quantity relation of the liquid supplynormally unaffected by a change in pressure in the flow path, and meansfor varying the quantity of liquid delivered to the flow passageindependent of the rate of displacement of said pump means.

8. A vapor generator comprising a furnace, a fluid flow passagecontinuous from liquid inlet to superheated vapor outlet and composed ofa plurality of long small-bore fluid flow conduit portions arranged forflow in parallel and having an extremely large ratio of heat absorbingsurface to cross-section, said path including vapor generating andsuperheating portions, means flring the furnace with elements ofcombustion in a manner incapable of forming a substantial fuel bed andoperable at a heat release rate and gas flow rate sufficiently high inrelation to the ratio of surface to cross section of said flow passageto evaporate and superheat the fluid before passing from the superheateroutlet, means at a location in advance of the superheating portion ofthe flow path and combining the fluid flow from a plurality of conduitportions for equalization of the heat content per pound of workingfluid, displacement pump means arranged to supply liquid positively tothe generator at a pressure substantially higher than the desiredworking pressure of the superheated vapor whereby the difference betweensupply and working pressures forces the fluid through the fluid flowpassage with a continuously decreasing pressure from liquid inlet tovapor outlet and with the pressure quantity relation of the liquidsupply normally unaffected by a change in pressure in the flow path, andmeans for varying the quantity of liquid delivered to the flow passageindependent of the rate of displacement of said pump means, a, portionof the heat absorbing surface of said flow path presenting asubstantially continuous heat absorbing wall area within the zone ofradiant heat to reduce to a minimum the heat storage capacity of thefurnace structure. Y

9. A method of generating superheated vapor in a vaporizer including afurnace and a flow path continuous from fluid inlet to superheated vaporoutlet and composed of a plurality of long, small-bore fluid flowconduit portions arranged for flow in parallel, said path including asteam generating and a superheating portion, said vaporizer having fluidforced therethrough from liquid inlet to superheated vapor outlet, whichcomprises supplying working medium to the vaporizer at a pressuresubstantially higher than the desired working pressure of thesuperheated vapor, utilizing the difference between supply and workingpressures to force said working medium through the vaporizer withcontinuously decreasing pressure from inlet to outlet, said flow pathhaving an extremely large ratio of surface to cross-section, releasingheat by combustion of fuel in the furnace and passing the gaseousproducts in heat transfer relation to said flow path at heat releaserate and gas flow rate sufficiently high in relation to the ratio ofsurface to cross-section of said flow path to evaporate and superheatsaid working medium in said flow path before it issues from the end 122.LlQoiD HEATERS & VAPORIZERSQ thereof, equalizing the heat content perpound of working medium entering the several conduit portions inparallel at a location in advance of the superheating portion of theflow path, operating the fluid forcing means to provide a continuoussupply of working medium at a rate at least equal to and a pressuregreater than the desired demand rate and pressure of superheated steam,and controlling the rate of working medium delivery to the flow pathindependent of the continuously imposed supply rate.

10. A method of generating superheated vapor in a vaporizer including afurnace and a flow path continuous from fluid inlet to superheated vaporoutlet and composed of a plurality of long,

small-bore fluid flow conduit portions arranged for flow in parallel,said path including a steam generating and a superheating portion, saidvaporizer having fluid forced therethrough from liquid inlet tosuperheated vapor outlet, which comprises supplying working medium tothe vaporizer at a pressure substantially higher than the desiredworking pressure of the superheated vapor, utilizing the differencebetween supply and working pressure to force said working medium throughthe vaporizer with continuously decreasing pressure from inlet tooutlet, said flow path having an extremely large ratio of surface tocross-section, releasing heat by combustion of fuel in the furnace andpassing the gaseous products in heat transfer relation to said flow pathat heat release rate and gas flow rate sufiiciently high in relation tothe ratio of surface to crosssection of said flow path to evaporate andsuperheat said working medium in said flow path before it issues fromthe end thereof, and equalizing the temperature of the working mediumentering the several conduit portions at a location in advance of thesuperheating portion of the flow path, operating the fluid forcing meansto provide a continuous supply of working medium at a rate at leastequal to and a pressure greater than the desired demand rate andpressure of superheated steam, and controlling the rate of workingmedium delivery to the flow path independent of the continuously imposedsupply rate.

HOWARD J. KERR.

